Explains how selective breeding and molecular biology methods could be used to produce a population of cats with the short legs. (i) Selective breeding E1: bases explanation on the assumption that the mutated allele is dominant. E2: breed short-legged offspring together or with mother. E3: any short-legged offspring will be either heterozygous or homozygous dominant. E4: to find out what they are, carry out a test cross ie breed with another normal cat (homozygous recessive). E5: if no normal size legs offspring occur (after multiple breedings), then it can be taken that the tested individual is homozygous for short legs. This cat can be used for future breeding. / Any cat that produces offspring with normal legs is heterozygous and shouldn’t be used for future breeding. (ii) Molecular Biology Transgenesis: pro-nuclear injection of isolated gene into fertilised egg cell, cell divides to form embryo, then embryo implanted into surrogate. OR Cloning: Somatic (ie 2N) cell from original female cat removed (nucleus has mutated allele), fertilised egg extracted from another cat, nucleus removed, and egg fused with donor cell/nucleus (electrical pulse used to stimulate this), egg divides to form embryo, then embryo implanted into surrogate.
6. Covers both selective breeding and one molecular biology technique. Explains correctly and fully how the methods can be used to produce a population of Munchkins. Minimal unnecessary information. 5. Correct and full explanation for one method, the other is substantially correct but lacks some details. 4. Both methods, substantially correct but lacking in coverage. Selective breeding must have E1. 3. Addressed both methods but issues with accuracy and/or coverage. Selective breeding must have E1. / One method well covered and correct, other hopeless (but has 1 or 2 correct ideas). 2. Some correct evidence for both methods. / Only one method answered but answered correctly and in detail. 1. Some correct biological ideas relevant to the question.
methods could be used to produce a population of cats
with the short legs.
(i) Selective breeding
E1: bases explanation on the assumption that
the mutated allele is dominant.
E2: breed short-legged offspring together or
with mother.
E3: any short-legged offspring will be either
heterozygous or homozygous dominant.
E4: to find out what they are, carry out a test
cross ie breed with another normal cat
(homozygous recessive).
E5: if no normal size legs offspring occur
(after multiple breedings), then it can be taken
that the tested individual is homozygous for
short legs. This cat can be used for future
breeding. / Any cat that produces offspring
with normal legs is heterozygous and
shouldn’t be used for future breeding.
(ii) Molecular Biology
Transgenesis: pro-nuclear injection of
isolated gene into fertilised egg cell, cell
divides to form embryo, then embryo
implanted into surrogate.
OR
Cloning: Somatic (ie 2N) cell from original
female cat removed (nucleus has mutated
allele), fertilised egg extracted from another
cat, nucleus removed, and egg fused with
donor cell/nucleus (electrical pulse used to
stimulate this), egg divides to form embryo,
then embryo implanted into surrogate.
biology technique. Explains correctly and fully how
the methods can be used to produce a population of
Munchkins. Minimal unnecessary information.
5. Correct and full explanation for one method, the
other is substantially correct but lacks some details.
4. Both methods, substantially correct but lacking in
coverage. Selective breeding must have E1.
3. Addressed both methods but issues with accuracy
and/or coverage. Selective breeding must have E1. /
One method well covered and correct, other hopeless
(but has 1 or 2 correct ideas).
2. Some correct evidence for both methods. / Only
one method answered but answered correctly and in
detail.
1. Some correct biological ideas relevant to the
question.